GM Service Manual Online
For 1990-2009 cars only

The design of the passlock™ system is to prevent the vehicle operation if the proper ignition key is not used in order to start the vehicle. The mechanical key, in normal operation, will turn the passlock™ lock cylinder. The passlock™ sensor will relay the passlock™ data to the body control module (BCM). The BCM will determine the validity of the passlock™ data. The BCM will send a code password to the vehicle control module VCM. When the VCM receives the correct code the VCM allows the fuel injectors to operate normally. The passlock™ system requires the VCM and the BCM to communicate the various functions in order to operate. These functions transmit over the class 2 serial data line CKT 1807. For an explanation of the class 2 serial data operation refer to Data Link Communications Circuit Description in Data Link Communications

Telltale Indication

Condition

ON constant for 3 seconds, then OFF

The bulb check occurs upon power-up (Ignition 1 and crank).

ON constant for 3 seconds, OFF momentarily, ON constant/ignition OFF

DTC (current) is set with the ignition ON (see DTC B2947, B2948, B2957 and B2958).

ON constant/ignition OFF

The TBC fuse is open or an open in CKT 1140

ON constant for 3 seconds, FLASH for 10 minutes, then OFF

Occurs when a Passlock™ sensor has been replaced and the ignition switch has been turned from the OFF position to the CRANK position. This sequence occurs 3 times.

FLASH with the ignition ON

The Passlock system is in a tamper mode (see DTC B2960 and B3033).

ON constant for 3 seconds, OFF momentarily, then ON constant for 10 minutes, then OFF

Occurs when a new BCM or a new VCM has been installed, and the ignition switch has been turned from the OFF position to the CRANK position. This sequence occurs 3 times.

ON constant for 3 seconds, OFF for 2 seconds, then ON constant

The IPC is unable to communicate with the BCM.